Cell lines from livers of transforming growth factor (TGF-beta1) null mice (knockout mice/KO) and wild-type mice were established and used as cellular models to investigate the functions of TGF-beta1. We have described an ultrastructural phenotype in the liver of null mice (C57BL6) with targeted disruption of TGF-beta1 gene), even though there are no visible abnormalities of the gross phenotype. TGF-beta1 has been localized in the mitochondria of rat liver (Heine et al. Cell Regulation 2: 467-471, 1991). This observation prompted further investigations into actions of TGF-beta1 that may be mediated through mitochondria. Ultrastructural pathology in the hepatic mitochondria of knockout mice included swelling, partitioning, division and abnormal phenotypes and patterns of cristae. Significantly increased numbers of mitochondria and intracytoplasmic canaliculi, previously described in breast carcinomas, were found in hepatocytes of null mice older than 3 weeks when maternally transferred protein was depleted. Increased numbers of Golgi complexes were seen in treated hepatocytes of null mice irrespective of age. The null hepatocytes in culture had numerous, highly refractile vacuoles which were shown to be autolysosomes on transmission electron microscopy. Between 4 and 6 hours following treatment of the null hepatocytes in culture with TGF-beta1, there was considerable reduction of the vacuoles and some motility of the hepatocytes. Studies on the effects of glucose on the colony-forming efficiency (CFE) of hepatocytes, from null and wild-type mice, showed a marked dose-dependent inhibition by the null hepatocytes compared to wild-type. MCF7 cells transfected with full- length and truncated TGF-beta showed abnormal mitochondrial phenotypes compared with control cells transfected with empty vectors. These findings suggest that TGF-beta is required for regulation of organelle structure and function and may have additional functions, hitherto unrecognized, that may involve organelles such as the Golgi complex and mitochondria. The primary liver cell cultures are being maintained for further studies on carbohydrate processing (glucose,fructose and galactose) and intracellular bioenergenetics.